As shown in FIG. 17, a forecast of energy consumption and resources supply indicates that all fossil carbon fuel will be exhausted before 2060 if current levels of energy consumption continue. This means that all of this world's energy resources, including uranium, natural gas, and coal, will be used up. In order to avoid such a situation, it is essential to utilize sustainable natural energy, and especially to utilize hydrogen energy, whose burden on the environment is low.
In order to transform natural energy into hydrogen energy, methods that use wind-power generation have been examined and applied on land. However, it is not realistic to meet all the energy needs of this country by using only on-land wind turbines, because wind turbines set up for that purpose would occupy one-fourth of this nation's land. In contrast, wind-energy-generating systems provided at sea can exploit natural energy across the vast expanses of the oceans.
Known float-type energy-generating systems include the fixed float-type system (hereinafter “FFT system”) and the sailing mega-float-type system (hereinafter “SMFT system”). As shown in FIG. 18, an FFT system is configured such that a floating body on which wind-power generators are mounted is moored in the sea. Although the areas where FFT systems can be set are limited due to the wind environment on the seas, FFT systems have high potential because of their low technical barriers. In FIG. 18, reference numerals 40 and 42 refer to a blade-fixation frame and a wind-turbine blade, respectively. An FFT system is not efficient in generating power in such areas, because winds in such areas are not constant throughout the year.
As shown in FIG. 19, an SMFT system is configured such that a very large floating body (mega-float) on which are mounted multiple wind turbines that generate, for example, around 5,000 kW per hour, is floated on international waters without mooring, electricity is generated by wind power, and the generated electrical energy is converted into hydrogen energy. An SMFT system has propulsion devices so that the SMFT system can maintain its position on the sea or be moved, as desired. However, due to financial cost-benefit considerations, the floating bodies on which wind-power-generation devices are mounted are very long, reaching a length of 2 km. As shown in FIG. 20 (it is assumed that a wind blows in the direction from the top to the bottom of the ordinate), an SMFT system has the wind and waves on its sides when it operates on the sea, and therefore the SMFT system moves up and down relative to the wind so as to prevent the floating body from being carried away by the wind. In order to obtain the energy required, hundreds of SMFT systems need to be provided. In FIG. 19, reference numerals 44 and 46 refer to a hull and a wind-turbine blade respectively.
As shown in FIG. 21, the maximum travel speed of an SMFT system is about 10 knots per hour if the SMFT system feathers the propellers of its wind turbines and uses its pod-propulsion devices (called thrusters) at full thrust. If a typhoon is expected to hit the SMFT system, it has to take evasive action in advance, in order to avoid damage to the propellers and other parts, because the travel speed of the SMFT system is low.
Consideration of the energy profit ratio (EPR) and the life cost analysis (LCA) requires that an SMFT system have long-term durability of about 100 years. Accordingly, the structural members of the floating body must be economical and prevent corrosion. Also, maintenance to prevent corrosion by seawater and adherence of marine organisms is necessary. Another problem of SMFT systems is that it is difficult to find a maintenance base for an SMFT system. Because there is no floating dock or building berth as long as 2 km, infrastructure building is also required in order to utilize an SMFT system.
As prior art, Patent Document 1 discloses a sailing energy-generating system that stores electrical energy that is directly or indirectly obtained from the revolution of electric generators on a vessel while the vessel sails. Patent Document 2 discloses an energy-storage device that stores electrical energy that is directly or indirectly generated by wind-powered generators or water-powered generators on a vessel. Patent Document 3 discloses a complex energy-generating system configured such that wind-powered generators are mounted on the deck of a vessel and water-powered generators that use running water are installed inside the vessel.
Although the invention of Patent Document 1 (generating energy by the sailing of a vessel) enables energy to be generated by water turbines that are rotated by the sailing of a vessel propelled by the wind, the shape of the sail is the same as that of a conventional sailing vessel, and therefore the sail is changeable depending on the prevailing wind. Accordingly, the vessel weaves in a strong wind, and therefore the invention of Patent Document 1 is not highly efficient in generating energy. Moreover, Patent Documents 2 and 3 (generating energy by using a combination of wind-powered generators and water-powered generators) also might not be highly efficient in generating energy, because those inventions have problems in that the direction in which the vessel advances is against the prevailing wind or ocean current.
Patent Document 1 Japanese Unexamined Patent Application Publication No. 5-236698
Patent Document 2 Japanese Unexamined Patent Application Publication No. 7-189884
Patent Document 3 Japanese Unexamined Patent Application Publication No. 8-261131